Millions of people desire to train and get in better shape. For many, this is difficult due to lack of time or the effort involved. Many systems have been developed to help people begin training or maximize their training efforts. For example, people read fitness magazines, follow workout programs, attend classes, hire personal trainers, etc. While some of these programs are tailored to individuals, they often fail to maximize a person's potential or cause frustration due to overwork. One cause of this is that many of these programs are not based on measures of a person's potential to perform exercise. Even for programs that uses some previous method to tailor programs to an individual, these methods has been difficult to implement and results have been inaccurate. Furthermore, training programs developed based on these measurements have failed provide correct levels of intensity and duration.
For example, VO2 is a measurement system that determines a maximum amount of oxygen a person can use. VO2 is measured by dividing an amount of oxygen inhaled per minute by an amount of oxygen exhaled per minute. Thus, VO2 based assessments require a user to be attached to an apparatus that can measure air intake and output and an amount of oxygen in the air. Furthermore, VO2 measurements are generally static for an individual and there is no clear way to translate a VO2 measurement into a duration or intensity level for training. Some techniques have been developed to provide workout guidelines based on heart rate measurements. However, these still require a specialized heart rate monitor attached to a person, are inaccurate, and do not correctly estimated limits on time or intensity training metrics.